For instance, a vehicle door frame is formed by butt-welding (corner-welding) a pillar member (upright pillar sash, door frame member) and a sash member (upper sash member, door frame member). In this welding process, TIG (Tungsten Inert Gas) welding or MIG (Metal Inert Gas) welding is generally used.
In this door frame member welding process, the occurrence of a weld bead (protrusion) at the welding area cannot be avoided. This weld bead appears on design surfaces of the pillar member and the sash member, thus being absolutely necessary to be grounded away to produce a smooth surface, and the weld bead was formerly removed manually by a worker. In addition to a roll-forming product of a metallic material, an extrusion-molded product of an aluminum alloy is also used as a door frame material for the purpose of weight reduction.